1. Field of the Invention
The present invention relates to a device for turning the front panel of a plate-like workpiece within a folder-gluer, that is to say a machine processing plate-like workpieces, such as cardboard or paper blanks, into "flat folded" and piled up boxes. These boxes can be rapidly converted into three dimensions afterwards. The blank size, as well as the creasing lines positioning the subsequent foldings, define the front and rear panels, the lateral panels, the bottom and cover elements of the box and, if required, the inner partitions. Some panels may also be provided with glue flaps.
The invention more particularly relates to a device for turning a rather large front panel of a blank, i.e. folding this panel from front to the rear, with respect to the travelling direction of the blank within the folder-gluer. Such a turning action of the front panel proves to be necessary, for example, when manufacturing record sleeves.
2. Brief Description of the Background Art
The turning of a small front flap is effected in a known manner by a device which is rather simple, comprising one or more hooks hanging in elastic manner from a crossbar, the lower end of these hooks being located in the travelling plane of the blanks.
The document FR 2,306,075 (corresponding to U.S. Pat. No. 4,052,932) describes an example of a known device for turning a larger front panel. This device comprises, on one hand, a folding crossbar located slightly above the travelling plane of the blanks, and whose horizontal V-shaped cross section is directed opposite to the travelling direction of the blanks. This device comprises, on the other hand, a series of lifting fingers located upstream of the crossbar and below the travelling plane and parallel to the crossbar. The fingers are actuated before the arrival of a blank by a piston, from an initial position below the plane to a raised slanted position directed towards the top of the crossbar. This operation may also be achieved by an air jet. As soon as the leading edge of the front panel is engaged above the crossbar, the fingers are brought back in to the lower position. The creasing line delimitating the rear edge of the front panel, remains flat on the lower conveyor. This creasing line yields to form a fold when arriving at the position of the crossbar. The front panel then is rapidly tilted by the stopping action of the crossbar onto the following intermediate panel. Then two panels pass together under the crossbar and into a calendar finishing the folding operation.
Folder-gluers are also known in which the turning device includes an upper vertical division plate associated with a lower upstream series of lifting fingers. In order to prevent the front part of the front panel from rebounding when ascending, possibly causing a premature folding, the upstream delivery side of the plate is provided with several vertical sliding rails held in front of the plate with a spacing slightly greater than the thickness of the blank. These sliding rails have the form of vertical bars whose lower ends are bent in the upstream direction in order to facilitate the engagement of the leading edge of the front panel, guided by the slanted lifting fingers. Moreover, the outlet of the upper upstream conveyor is positioned at a chosen distance with respect to the plate in such a manner that the front panel, initially arriving in the horizontal position, can bend in order to raise into the vertical position against the plate without breaking, but such that the rear creasing line immediately yields to produce a fold upon arrival at that position. This fold pass under the plate in order to be seized afterwards by the downstream conveyor, the front panel being then pulled downwards and pushed against the following intermediate panel.